"Sludge" up U Joint? Odd Situation!

[SwampSurvivor]

So I have a bit of Lift in my cherokee. The driveline angles on the rear driveshaft aren't that bad from what I've been told.

If I just drive to and from work, I can get unlimited miles out of the front u joint in my rear driveshaft.

If I have an extended highway run or drive it 40 or 50 miles straight, the U joint starts vibrating.

If I grease the U joint ON the vehicle, it doesn't help. When I pull it off, I can see that the U Joint is nearly set up. However, if I take it off, grease it and work it through it's FULL range of motion ... it operates like new.

When I grease them, I wipe off all of the extra grease. But what I notice when pulling off the shaft is that the U joint is coated in oil.

Is it possible that I'm making the oil actually come out of the joint leaving just the carrier in there?

 

[Donald]

A U-joint should only need greasing a few times over the vehicles life. I would guess you have exceeded the angle at which the U-joint should be operated.

 

[Food Scientist]

If you over grease a U-joint the base oil will leave the grease (why you have an oily U-joint) leaving only the additives to perform the work. Thickeners and any EP additives alone will not lubricate properly. Also what Donald said.

 

[jeepman3071]

At 3.5" of lift on a '97 or newer Cherokee, you should have a slip yoke eliminator kit and a new driveshaft. My 2000 had driveline issues at only 2" of lift. I currently have a 1" transfer case drop kit installed, which has helped, but its temporary until I can afford the SYE.

The older Cherokees had a different style output shaft on the transfer case, and some could get away with 4" of lift and only a transfer case drop. The '97 and newer have a different output shaft which makes driveline problems more likely. Some of the Cherokees with the Up Country package (1" lift) had to have transfer case drops installed at the dealer when they were new. Not having the right driveline angles will cause you to eat u-joints.

 

[Kestas]

The u-joint is overheating, causing oil to bleed out of the grease. You could look for a more temperature resistant grease to help mask the problem.

 

[SwampSurvivor]

Originally Posted By: jeepman3071
At 3.5" of lift on a '97 or newer Cherokee, you should have a slip yoke eliminator kit and a new driveshaft. My 2000 had driveline issues at only 2" of lift. I currently have a 1" transfer case drop kit installed, which has helped, but its temporary until I can afford the SYE.

The older Cherokees had a different style output shaft on the transfer case, and some could get away with 4" of lift and only a transfer case drop. The '97 and newer have a different output shaft which makes driveline problems more likely. Some of the Cherokees with the Up Country package (1" lift) had to have transfer case drops installed at the dealer when they were new. Not having the right driveline angles will cause you to eat u-joints.


I plan on doing a SYE at some point. That's part of the reason I've only put 500 miles on it since October.

Even worse than the rear shaft is I keep eating front Cardan joints with the transfer case drop.


Originally Posted By: Kestas
The u-joint is overheating, causing oil to bleed out of the grease. You could look for a more temperature resistant grease to help mask the problem.


It does get EXTREMELY hot to the touch!

 

[Zaedock]

I recommend buying an angle finder and determine if you need a slip yolk eliminator and new rear shaft. It sounds like the joint is overheating on long trips due to the angle.


Regarding grease, there is no such thing as over greasing. Greasable u-joints are supposed to be purged via the bearing cap seals. Slowly pump in fresh grease until you see fresh grease ooze from the cap seals. Wipe off the excess. You'll need to do it more often if you off road and directly after a deep water crossing.

A synthetic grease (I use Valvoline Synpower bearing grease) may be a possible temporary solution.

 

[SwampSurvivor]

Originally Posted By: Zaedock

Regarding grease, there is no such thing as over greasing. Greasable u-joints are supposed to be purged via the bearing cap seals. Slowly pump in fresh grease until you see fresh grease ooze from the cap seals. Wipe off the excess. You'll need to do it more often if you off road and directly after a deep water crossing.


All of my U Joints are greasable for that reason. It does see off road use.

The one at the transfer case usually doesn't see water, though ... I don't think I've ever had it that far in water! haha

 

[Zaedock]

In that case, you may be better off with solid joints in the driveshaft. The Spicers have several seals that click on and hold the grease better.

It's six of one, half dozen of the other though, as the true issue is probably the angle. The SYE would fix your front DC driveshaft issue too, as you could remove the t-case drop and restore it to the proper angle.

Measure your front shaft too. I run a Cherokee DC front shaft cut down as my rear. It might be cheaper to have a bit of tube added and you could install a "hack & tap" SYE kit (drill and tap the existng mainshaft). They're about a hundred bucks +/-.

 

[SwampSurvivor]

Originally Posted By: Zaedock
In that case, you may be better off with solid joints in the driveshaft. The Spicers have several seals that click on and hold the grease better.

It's six of one, half dozen of the other though, as the true issue is probably the angle. The SYE would fix your front DC driveshaft issue too, as you could remove the t-case drop and restore it to the proper angle.

Measure your front shaft too. I run a Cherokee DC front shaft cut down as my rear. It might be cheaper to have a bit of tube added and you could install a "hack & tap" SYE kit (drill and tap the existng mainshaft). They're about a hundred bucks +/-.


I'm thinking Hack n Tap is what I'm going to do. Worst comes to worst, I just go to the local JY and buy another 231 TCase.

It's a close one ... I may or may not be able to use the front shaft; I think it may be too long. I would be okay, but if I have a lot of weight in the back I may end up putting it through the case.

I'd also stop getting stuck on the @#$@#$ crossmember off road.

 

[mechtech2]

Match the angles of the two U joints. Shimming is how.

 

[Zaedock]

Originally Posted By: Miller88
It's a close one ... I may or may not be able to use the front shaft; I think it may be too long. I would be okay, but if I have a lot of weight in the back I may end up putting it through the case.


That's actually good, as it's cheaper to shorten a shaft than to lengthen it.

The last driveshaft I cut/shortened myself came out nice. I had it spun to 3,000 rpm and it needed no weight. The driveshafts for my rock buggy are going to be 1/4" thick square tube.

 

[SwampSurvivor]

Didn't know that! I'm going to play around and see what I find. Different transmissions and axles had different length driveshafts.

The driveshaft from a 96 Auto HP is a tad bit shorter than my 00 auto LP



Originally Posted By: mechtech2
Match the angles of the two U joints. Shimming is how.


I have the rear axle shimmed - the rear u joint does nothing as the driveshaft sticks straight out. all of the work is done by the front. I'm sure I'm losing harmonics with it happening in the front.

If I were to go SYE, I'd have the cardan joint woring.